# AdGuard Home DNS Auto-Registration

Automatically registers `{hostname}.home.dustin.coffee` → its own IP with AdGuard Home
DNS rewrites on boot. Designed for the `home.dustin.coffee` home lab domain.

## How It Works

1. On boot (via systemd oneshot service), the script determines the host's short hostname
   and primary IPv4 address
2. It authenticates with the AdGuard Home API at `172.20.1.1`
3. It checks if a DNS rewrite for `{hostname}.home.dustin.coffee` already exists:
   - **No entry**: creates a new rewrite pointing to the current IP
   - **Entry exists with same IP**: skips (idempotent)
   - **Entry exists with different IP**: updates the rewrite (handles renumbering)
4. Verifies the rewrite was applied successfully

The IP detection skips Docker bridges, Tailscale interfaces, and loopback to find the
host's real primary address.

## Deployment

### On a new LXC/VM

```bash
# Copy the agent directory to the target host
scp -r adguard-register/ user@target-host:/tmp/

# SSH in and install
ssh user@target-host
cd /tmp/adguard-register
sudo ./install.sh
```

### Manual registration (one-off, no install)

```bash
sudo /usr/local/bin/adguard-register
```

### Uninstall

```bash
sudo /path/to/adguard-register/uninstall.sh
```

## Requirements

- `curl` — for API calls
- `python3` — for JSON parsing
- `systemd` — for boot-time execution (or use `@reboot` cron as fallback)
- Network access to `172.20.1.1:80`

## Files

| File | Purpose |
|------|---------|
| `adguard-register.sh` | Main registration script |
| `install.sh` | Copies script to `/usr/local/bin/` and sets up systemd service |
| `uninstall.sh` | Removes the service and script |
| `README.md` | This file |

## Troubleshooting

### Check service status
```bash
systemctl status adguard-register
journalctl -u adguard-register
```

### Test manually
```bash
sudo /usr/local/bin/adguard-register
```

### Common issues

- **"Failed to authenticate"**: Verify AdGuard Home is running at `172.20.1.1`
  and credentials are correct
- **"Could not determine primary IPv4 address"**: Ensure the host has a
  non-loopback, non-Docker, non-Tailscale IPv4 address
- **"Verification failed"**: The API accepted the change but the read-back
  didn't match; check AdGuard Home logs
- **Python3 not found**: Install with `apt install python3` or equivalent

## AdGuard Home API Reference

- Base URL: `http://172.20.1.1/control/`
- Auth: `POST /control/login` with `{"name":"...","password":"..."}`
- List rewrites: `GET /control/rewrite/list`
- Add rewrite: `POST /control/rewrite/add` with `{"domain":"...","answer":"..."}`
- Update rewrite: `POST /control/rewrite/update` with `{"target":{"domain":"..."},"update":{"domain":"...","answer":"..."}}`